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Post harvest handling practices to prevent losses

by William and Mary Weaver

“At harvest, the quality clock is ticking. Post-harvest losses can be staggering. I decided to specialize in post-harvest handling when I saw how much of the loss could be prevented,” stated Dr. Steve Sargent of UF/IFAS Extension.

The waste is huge. From field to retail in the United States and other developed countries, losses of unmarketable produce can be as high as 23 percent and average 12 percent. Additional losses in retail and food service can be as high as 30 percent with an average of 20 percent. And much of the loss is avoidable, according to Dr. Sargent.

In addition to the outright loss, poor post-harvest handling also leads to quality deterioration. What does that mean for your profits? Quality losses include loss of nutrients over time, a big concern with today’s consumers. Loss of nutrients can result from a simple thing such as not cooling promptly after harvest.

Then there are home- and restaurant-level losses. Leaves and other deteriorated parts that are no longer edible must be trimmed and discarded.

In dollar terms, according to the USDA, an estimated $162 billion worth of vegetables is lost every year, and about $38 billion in fruit because it becomes inedible. “Some fairly simple changes could be made, in both large and small operations that could make a big dent in that waste, returning higher profits to the growers,” stated Dr. Sargent.

The suggestions that follow will focus on better postharvest handling of peppers, eggplant, and other highly perishable fruits, such as summer squash.

For example, cutting or clipping stems of peppers and eggplant lessens desiccation and wounding, and consequently, the entrance of pathogens through the stem.

Harvest peppers and eggplant when the fruit is still shiny and bring the filled picking containers promptly to shade and the packing station. Train workers and give them incentives to handle fruit gently. Damage from impact bruising will not always be apparent immediately. A couple of days later, though, the natural wax of the outer layer of the skin will show damage, leading to desiccation. In all these fruits, over time, a fingernail puncture will stimulate accelerated ripening in the punctured area. This is especially a problem in tomatoes. The damaged area will color up while the rest of the fruit remains green.

Compression bruising can be an important cause of decay in peppers packed in crates. We’ve all seen it. The crate is packed too full, and a worker struggles to force the lid shut. The top fruit may crack, and those on the bottom will be bruised. Overfilling a crate may seem like a small thing, but sometimes correcting seemingly small mistakes can make a big difference in the quality and shelf life of your product. Single layer shipping containers can be worth the cost for the more valuable colored peppers to prevent damage during shipping.

A field packing station observed by Dr. Sargent in the Immokalee, FL area avoided a lot of potential problems. “The banana peppers were picked into half-height bins (cutting compression bruising in the bottom), transferred into water (no impact bruising), then moved down a belt for sorting.

The sorted peppers were chilled quickly in a long, forced air tunnel, taken out and packed immediately for fresh market or processing at the other end of the tunnel. “It was a portable operation,” commented Dr. Sargent, “right at the side of the field.” With it, the grower avoids many of the potential causes of post-harvest losses.

If you’re thinking of building or remodeling a packinghouse, the best advice, according to Dr. Sargent, is to keep the packing line layout as straight as possible. Avoid turns. “With every turn, you can abrade fruit, or bruise it where it drops to turn a corner,” he said. Design your packinghouse for unrestricted flow.

Larger tomato growers are reducing impact bruising by designing their packing lines to receive large gondolas. The fruit is washed out of the gondola through a rear gate and into a large flume system.

“We measured the amount of damage to the fruit, and found this is truly an excellent way to get fruit onto the packing line with minimal damage,” explained Dr. Sargent, “As the fruit floats through the system, it can be divided into separate packing lines.”

This system is not advised for bell peppers destined for fresh market, since openings around the calyx could potentially allow water to enter and cause decay. “It’s a great system to prevent bruising in summer squash, however,” he added.

A word of warning regarding water temperature when fruits will be immersed: The water should be 10 degrees F. warmer than the fruit to minimize water infiltration and the entrance of pathogens. In addition, the water needs to contain a sanitizer. Sargent recommends 150 to 200 ppm of free chlorine at roughly 6.5 to 7.5 pH. The fruit should be in the water no longer than two minutes, then should be quickly rinsed and excess water blotted off before it enters the packing area.

Not everyone can afford a water transfer system to minimize bruising, but a little care can greatly reduce impact bruising in a dry transfer system. “Often we see an unrestricted six-foot drop into a padded hopper.” The padding is very nice for the first fruit that actually hit the padding, but later-dropped fruit hit other fruit with quite a bit of force. “A better practice is for the bin to be very gradually inverted, with a brush pushing the fruit very gently onto the packing line,” continued Dr. Sargent.

“In Mexico, we saw an auto dumper in operation that slowly and gently tilted the small field lugs so the bell peppers slowly poured out directly onto the packing line,” where they went over brush rollers with overhead spray. With an automated dumper, the dumping speed will be the same every time. When a worker controls each dump, vigilance in the dumping area is important for management, so that dumping is consistently slow and gentle and not rushed. Minimize drop heights as much as possible to minimize stem punctures and fruit-to-fruit impact.

If you use the so-called “stop light” consumer pack for peppers, keep in mind that although this is a popular pack that catches consumers’ attention, internal condensation within the plastic overwrapped pack can lead to decay because the pack is sealed.

Peppers and eggplant hold best at 48-50 degrees, at a high (but not 100 percent) humidity. Of all possible cooling systems, forced air or tunnel cooling is the best for cooling highly perishable vegetables such as peppers and eggplant quickly and evenly. The more quickly they are cooled to the optimal storage temperature, the longer their potential shelf life will be.

In the end, implementing some simple changes in handling can lead to a sizeable reduction in losses.

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